The present invention relates to a method of processing video signals which are sampled according to a sampling pattern having at least one omitted element which differs from picture frame to picture frame, including, inter alia, a switched video signal selection operation.
The invention also relates to a video signal converter for putting the method into effect.
The direct broadcasting of high-definition television pictures requires a passband which is not compatible with the present-day possibilities of the transmission channels. It is therefore necessary, in order to broadcast such pictures, to reduce this passband by sub-sampling.
In order to obtain nevertheless, on reception, a picture quality which is close to the starting quality in the case of still picture, the currently proposed sampling structures (see for example the laboratory report "A single channel HDTV broadcast system: the MUSE, by Y. Ninomiya et al., no. 304, September 1984, distributed by the firm of NHK, Tokyo, 157 Japan) provides the use of a first sampling pattern for even pictures and a different one, interlaced with the first, for the odd pictures. The complete resolution is then obtained again on reception by accumulating the samples of the two consecutive pictures. In the case of moving pictures, an interpolation in the current picture is furthermore provided.
The periodical "Radio Mentor Elektronik", no. 5, 1975, pages 196, describes a method and an arrangement for processing video signals in which, more specifically, a video signal selection operation is provided. This selection operation, which is associated with a subsequent decision operation, is realized in a non-linear filter which, when made operative, renders it possible to obtain a picture of a correct quality. It is, however, a known fact that such processing methods, using motion detection, nevertheless generate faults such as the flicker phenomenon in the switching points.